1. Field of the Invention
This invention relates to disk drive suspensions comprising load beams and flexures in which the flexure tongue is limited in its travel by a limiter structure. More particularly, the invention relates to the snap-in connection of the flexure tongue-borne limiter structure to the load beam in a movement requiring only the pressing together of the load beam and flexure. Relative longitudinal movement of the flexure or flexure tongue and the load beam, usually required with flexure tongue-borne limiter structures that insert into the load beam with a longitudinal axial movement, is obviated, with resultant increased production rates and reduced incidence of defects.
In the invention, a snap-fit disk drive suspension assembly is provided comprising a load beam having a slot and secured to the load beam a flexure having a cantilevered tongue opposing the load beam and adapted to carry a slider. The invention structure is suitably formed on the tongue and sized to limit excursions of the tongue relative to the load beam. The limiter structure comprises a normally upright, resilient tab offset from a cooperating slot. The tab, typically carried by the flexure is similarly resilient so as to be deflectable bodily by the load beam in which the cooperating slot is formed until the slot registers with the tab. The limiter tab thus snaps into the slot in a deflected condition and immediately returns to an upright condition thereby engaging the tab with the load beam at the slot edge margin. The so-fixed limiter structure thus limits the flexure tongue excursions, is placed in position without relative longitudinal axial displacement of the load beam and flexure, and once so snapped into place is engaged there permanently.
2. Related Art
Limiter structures or more simply limiters are mechanical devices that block unwanted movement of a flexure tongue as it carries the suspension slider, usually by blocking undue movement with a structure supported by the flexure, the load beam or both. Workers in the art of limiter structures have attempted to meet progressively more difficult requirements for advanced disk drive suspensions. Initially, the main criterion was shock resistance, then load/unload capability became important. In a suspension shock resistance is the ability of the suspension to limit the angular stroke and/or the displacement of the flexure relative to the load beam so that the slider does not damage the disk when the lift off shock threshold is surpassed. In cases where the slider design permits, in the simplest terms, this means that the suspension does not allow the slider to lift off the disk, thus controlling the slider movement directly. But, as the shock threshold requirement increases, the slider will eventually be lifted off the disk during a shock event. Thus, the problem becomes one of controlling the slider motion during the time the slider is no longer in contact with the disk. In this context, non-contact of the slider with the disk refers to the slider being more than a few times farther separated from the disk than it is in the steady-state flying condition. During flying, the slider may be from less than one microinch to several microinches from the disk; this is considered to be in contact. Not in contact is a separation of 100 microinches or more, possibly up to a few thousandths of an inch.
During the time the slider is not in disk contact, the slider motion is slightly restrained by the action of the flexure and the load beam acting on the mass of the slider. Since, however, the slider is greatly energized by a shock event, the soft flexure and load beam springing is unable to completely control the slider motion.
In load and unload cycles, the load beam and flexure are further used in a reverse role, i.e. to pull the slider away from the disk instead of holding it against the disk.
The two requirements of shock resistance and load/unload cycling have been addressed in a variety of load beam and flexure designs, e.g. U.S. Pat. Nos. 5,771,136; 5,526,205; and 5,570,249. In general, the prior art has emphasized solving either the shock problem or the load/unload cycle. Where shock resistance is the primary consideration, limiters have been proposed that contact the flexure near the center of mass of the slider, or if that is not possible, contacts the flexure on both left and right sides on a transverse line that crosses through the center of mass of the slider or near to it. Where load/unload cycling is the primary consideration, the preferred location of the limiter is near the leading edge of the slider because then the limiter restricts the ability of the nose to drop to far below the correct attitude, and this ensures that the slider will load and unload in the nose-up (leading edge-up) condition.